1. Field of the Invention
The invention relates to a data input or output apparatus for a central data processing system, comprising electromechanical elements such as motors or magnets, an electronic control device for the exchange of data and control signals with the central data processing system and for generating internal control signals for the activation of the electromechanical elements, and also comprising a power supply device for supplying the electric energy for the electromechanical elements, said apparatus further comprising a measuring device for measuring a supply current drained from the power supply apparatus and supplying measurement values, said apparatus also comprising comparing means for comparing the measurement value to a reference value.
An apparatus from this kind is described in U.S. Pat. No. 3,839,628, which apparatus is provided with means for measuring the frequency spectrum distribution of the electric power applied to the drive motor during a standard operating cycle of the system.
In an apparatus of this kind it is customarily desirable to test the operability at frequent or regular intervals before the occurrence of malfunctioning which unnoticeably causes incorrect results or serious damage. A test of this kind can be performed during regular inspections by service personnel, but is then very complex and expensive. Therefore, a maximum amount of automatic functional testing by the apparatus itself is desirable.
2. Description of the Prior Art
In electronic data processing systems it is known to perform automatic functional testing of the electronic parts by the execution of a test program, notably when the system is switched on. Therefore, except for the test program or its space in the program memory, electronic systems of this kind require no or only few additional devices for the execution and evaluation of a complete test.
The drawback of the known apparatus is that it is possible to test only one electromechanical element, and that the test operation has to be done during the operating cycle of the system. This implies that the user needs to wait for a whole operating cycle in order to get some results of the test operation.